Before human disease can be discussed, the meanings of the terms health, physical fitness, illness, and disease must be considered. Health could be defined theoretically in terms of certain measured values; for example, a person having normal body temperature, pulse and breathing rates, blood pressure, height, weight, acuity of vision, sensitivity of hearing, and other normal measurable characteristics might be termed healthy. But what does normal mean, and how is it established? It is well known that if ... (100 of 23,344 words)